Study on the influence of annealing temperature and ferrite content on the structural and magnetic properties of x(NiFe2O4)/(100 − x)SiO2 nanocomposites

Magnetic nanocomposites of nickel ferrite nanoparticles uniformly dispersed in the silica matrix have been synthesized successfully by a sol-gel process using tetraethylorthosilicate (TEOS) and metallic nitrates as precursors. In addition, the influence of the annealing temperatures, varying from 400 to 900 °C, and NiFe2O4 contents, x(NiFe2O4)/(100 − x)SiO2 (10 ≤ x ≤ 60 wt.%), on the structural and magnetic properties of the nanocomposite samples have been investigated. The studies carried out using XRD, FT-IR, TEM, STA (TG-DTG-DTA) and VSM techniques. The results indicated that the structural and magnetic properties of the samples showed great dependence on the variation of the particle size caused by the annealing temperature and NiFe2O4 content. The crystallization, saturation magnetization Ms and remenant magnetization Mr increased as the annealing temperature and NiFe2O4 content increase. But the variation of coercivity Hc was not in accordance with that of Ms and Mr, indicating that Hc is not determined only by the size of NiFe2O4 nanoparticles. TEM images showed spherical nanoparticles homogeneously dispersed in the silica network and were uniform in both morphology and particle size distribution with sizes of 10-15 nm. The results showed that the well-established silica network provided nucleation locations for NiFe2O4 nanoparticles to confinement the coarsening and aggregation of nanoparticles. The synthesized nanocomposites with adjustable particle sizes and controllable magnetic properties make the applicability of nickel ferrite even more versatile.